The one remarkable thing about the Fringe theatre programme this year is the sea change that terrorism in the Western world has wrought in the creative consciousness of the United States and, to a lesser extent, in Britain.
You need look no further than the American High School Theatre Festival which, year after year, is by far the most significant contributor to the Edinburgh Fringe. For more than a decade this group of schools and colleges, representing the year's cream of youth theatre, has been a wonderful shop window for what the US taught the world and does best, the all-singin', hoofin', "tears and smiles" musical.
While British schools and youth theatres have often gnawed away at drugs and truancy, bullying and deprivation, the chorus lines of precociously talented and physically well-developed American teenagers have danced and sung their way through 20th-century American history.
But this year it is different. Not that the musical has been entirely swept away - Aida, for example, (not the opera but the Broadway musical from Disney with a pop-rock score by Elton John) is briefly at the Church Hill - but two different, cooler breezes are blowing through their programme.
The chillier of the two comes more or less straight from the Twin Towers.
Omnium Gatherum is a dinner party in the home of one of New York's famous hostesses. Taking place some time after 911, it is not the wise-cracking event it used to be. Apart from praising the food, the guests discuss terrorism, but one of the may make a special contribution.
In the manner of reportage, With Their Eyes: A Look at Ground Zero is a chronicle of some of the first-hand stories from witnesses of an event that, the theatre significantly comments, "challenged the human spirit and changed the world".
Hand in hand with the need to come to terms with terrorism is a detectable willingness to relate to the world beyond the United States and, this being the Edinburgh Festival, particularly with Scotland and the rest of the UK.
We are all instinctively parochial and Americans, having a whole half-continent to be parochial in, often reveal an ignorance and indifference to Britain that can be the despair of tourists. This year, however, there is a reaching-out that almost seems like a special relationship. Syracuse University is bringing A Remarkable Story, "a lyric drama on the aftermath of the Pan Am Flight 103" (known to us as the Lockerbie disaster), showing how "a Scottish village turned an act of terrorism into an act of love".
The American High School Theatre Festival also offers "an original musical pastiche' called Hats, which investigates the life of J. D. Fergusson, the Scottish colourist who died in 1961. Inspired by a gallery showing some of Fergusson's sketches, the songs turn around his fascination with headgear in the creative milieu of the early 20th century.
Some kind of artistic "hands across the ocean" is promised by HWS Rembiko Project's Gilbert and Sullivan's The Gondoliers: County USA, coming, as it does, with allusions to "George W and Condi importing democracy to the Middle East ... God Bless America!" Not one for the purists, I suspect.
Unusual fun at the expense of their compatriots comes from the High Schools' An American in Edinberggggg, which actually offers political and social satire of US citizens and their behaviour during the festival. It used not to be like this.
Coming to the Fringe is an intensive, expensive experience in arts education, and happily the US schools are still able to afford it. It is a very different story for the home-grown talent. Every year, well-known names are falling off the lists, as economies bite deeper and costs rise.
Of schools, only the wealthier fee-payers, such as Westminster and Gresham's, can make a fist of it, though Grangemouth High manages one performance of Juliet's Tomb. Two or three youth theatres from the north of England are establishing a presence, but the Scottish representation is disappointing.
Three groups from around Edinburgh make what amount to hardly more than token appearances: Dundee Rep Youth Theatre (Maybe Tomorrow, a new play by Tim Primrose) come for one day, and West Lothian Youth Theatre (The Tempest) for two; only Forth Youth Theatre, at home on Ferry Road, can afford to give their Sweeney Todd a proper run.
Edinburgh Festival Fringe, August 7-29 tel 0131 226 0000 www.edfringe.com